Controlling and recording apparatus for a liquid dispenser

ABSTRACT

Apparatus used with a gasoline pump controls operation of the pump and records the amount of gasoline dispensed thereby to each of a number of customers or users. Each of the customers has his own key for a specific lock of the apparatus. When the key is turned, a recording device indicates the amount of gasoline dispensed and a switch is closed to ready the gasoline pump for operation when the gasoline nozzle valve is operated by the user. The quantity of gasoline consumed by each customer is periodically noted and the customers are billed accordingly. The apparatus is less expensive to manufacture and, at the same time, is more reliable than devices heretofore proposed for the same general purpose.

United States Patent Clark et al.

[54] CONTROLLING AND RECORDING APPARATUS FOR A LIQUID DISPENSER [72] Inventors: Alonzo R. Clark, 100 Maple Street; Robert W. Bloom, 108 E. Lynn Street,

both of Stryker, Ohio 43557 [22] Filed: Feb. 11, 1971 [21] Appl. No.: 114,486

[52] US. Cl ..235/94 R, 235/91 PR [51] Int. Cl ..B67d 5/22 [58] Field of Search ..235/94 R, 94 A, 91 PR; 222/23, 222/25, 26

' [5 6] References Cited UNITED STATES PATENTS 2,174,656 10/1939 Hanrahan et a1 ..235/91 PR 2,522,845 9/1950 Stevens ..235/94 R 2,995,275 8/1961 Brice ..222/26 3,026,032 3/1962 Settlemire ..235/94 R l8 tit [is] 3,657,523 Apr. 18, 1972 Primary Examiner-Richard B. Wilkinson Assistant ExaminerStanley A. Wal AttorneyAllen D. Gutchess, Jr.

[ 57] ABSTRACT Apparatus used with a gasoline pump controls operation of the pump and records the amount of gasoline dispensed thereby to each of a number of customers or users. Each of the customers has his own key for a specific lock of the apparatus. When the key is turned, a recording device indicates the amount of gasoline dispensed and a switch is closed to ready the gasoline pump for operation when the gasoline nozzle valve is operated by the user. The quantity of gasoline consumed by each customer is periodically noted and the customers are billed accordingly. The apparatus is less expensive to manufacture and, at the same time, is more reliable than devices heretofore proposed for the same general purpose.

10 Claims, 6 Drawing Figures PATENTEDAPR 18 I972 MMWH SHEET 1 BF 3 0000000000 1', occooooooo I N VE NTORS BY 5/1/51 00M wQM PATENTEUAPR 18 I572 SHEET 2 BF 3 INVENTORS 4. A? 614% 5 A. h! 5L 00M $145M 4770/?A/EV PATENTEUAPR 18 [512 3, 657, 523 SHEET 3 OF 3 A rraw/va CONTROLLING AND RECORDING APPARATUS FOR A LIQUID DISPENSER This invention relates to apparatus for controlling and cumulatively recording the amount of liquid dispensed by a dispenser, and particularly the quantity of gasoline dispensed to each of a number of customers over a period of time.

An entrepreneur owning a gasoline pump and a controlling and recording unit according to the invention can supply a key to each of a number of customers or users who use large quantities of gasoline. The customer engages a recording device and closes a switch to actuate the gasoline pump when his key is inserted in the unit and turned. The gasoline dispensed is cumulatively recorded for each customer and noted by the owner from time to time who then bills the customer accordingly. There is no attendant at the gasoline pump, with the customer dispensing the gasoline himself. This reduces expenses and enables the gasoline to be sold at a lower rate than at a conventional gas station. Further, the pump is available at any time, day or night, for the customers.

The controlling and recording unit embodying the invention has a plurality of locks to accommodate a plurality of customers. When the customers key is inserted in the appropriate lock and turned, an individual recording device for that customer is mechanically connected with a computer mechanism of the gasoline pump and substantially at the same time, a switch in the unit is operated to energize the dispensing pump of the gasoline pump. The manner in which the individual recording devices are engaged with the computer mechanism assures reliability of the recording phase of the unit. Also, only one switch need be employed for each row of locks of the controlling and recording unit. Consequently, the overall unit is relatively simple and also is inexpensive to manufacture, at the same time achieving a high degree of reliability.

It is, therefore, a principal object of the invention to provide a controlling and recording unit for a gasoline pump which is less expensive and more reliable than those heretofore known.

Other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawings, in which:

FIG. 1 is a somewhat schematic, overall view in perspective of a gasoline pump and a controlling and recording unit according to the invention;

FIG. 2 is a somewhat schematic front view of the controlling and recording unit of FIG. 1, with the doors removed;

FIG. 3 is an enlarged fragmentary front view, with parts broken away, of the unit of FIG. 2;

FIG. 4 is an enlarged view in horizontal cross section taken along the line 44 of FIG. 3;

FIG. 5 is a detailed side view of a switch and mounting arrangement of the unit; and

FIG. 6 is a view in transverse cross section through a recording device of the unit.

Referring particularly to FIG. 1, a controlling and recording unit according to the invention is indicated at I0 and is shown mounted on top of a gasoline pump or dispenser 12. The pump 12 can be any of several commercially known types and includes a hose 14 with a nozzle 16 and a hand-operated valve. The gasoline pump is equipped with an electrically operated dispensing pump for supplying gasoline through the hose l4 and the nozzle 16, and also has a computer mechanism for indicating the monetary value of the gasoline being pumped on a dial 18 and the quantity in gallons on a dial 20.

Referring particularly to FIG. 2, the recording and controlling unit has forty stations, indicated at 22, each station including a lock 24 and a window opening 26. The cumulative amount of gasoline dispensed by a particular customer having a key for the corresponding lock 24 appears in the window 26. As the customer needs gasoline, he inserts and turns his key in the lock 24 and dispenses as much gasoline as desired. Each time one of the locks 24 is turned, the dispensing pump in the gasoline pump 12 is actuated through switches 28 (FIGS. 2, 3,

and 5) and a meter or recording device 30 is mechanically engaged with the computer mechanism of the pump 12 to record the quantity dispensed.

Periodically, typically each month, the quantity of gasoline consumed by each customer is noted through the window 26 and a bill is sent to each customer for the amount of gasoline dispensed for the month. Since little labor is involved, a lower price per gallon of gasoline can be charged. Further, the gasoline pump 12 is available 24 hours a day.

Each of the locks 24 extends through an opening 32 (FIG. 4) in a cover 34 of a housing 36. The cover 32 preferably is hinged at 37 to one side of the housing 36 and has locks 38 (FIGS. 2 and 4) at the other edge to hold the cover closed. The cover 34 also has doors 40 (FIG. 1) mainly for protection from the weather. These doors can be equipped with springs or spring-loaded hinges to cause the doors to always be urged shut.

There are 40 of the stations 22 in the specific unit 10, as shown in FIG. 2. The stations are arranged in four vertical rows of 10 each with the recording devices 30 and the windows 26 vertically arranged in one row and the locks 24 arranged in a parallel row. While there is one of the devices 30 for each of the stations 22, there is only one of the switches 28 for each of the two outer rows of stations and one of the switches for both intermediate rows of stations, thereby necessitating only three of the switches 28 for all 40 of the stations 22. This substantially reduces the cost of the overall unit 10, increases the reliability, and lowers the maintenance by reducing the number of operating components.

Referring now in more detail to the components of each of the stations 22, the lock 24 has a threaded portion 42 (FIGS. 3 and 4) extending through a mounting strap 44 which extends vertically in the housing 36 and holds all of the locks in one of the rows, there being four of the straps 44 for the four rows. The threaded portion 42 of the lock 24 and the opening through which it extends in the strap 44 are non-circular to prevent the shell of the lock 24 from turning. The mounting strap 44, in turn, is affixed to a main mounting plate 46 in the housing 36 by suitable fasteners 48. The mounting plate 46 is affixed to a back wall 50 of the housing 36 by adjustable threaded rods or fastener assemblies 52 (FIG. 4). With this arrangement, the mounting plate 46 can be adjusted relative to the back wall 50 to control the extent to which the locks 24 extend through the housing cover 34.

The lock 24 is mounted on the strap 44 by a lock nut 54 (FIG. 4) and beyond this is an elongate or cam member 56 (see also FIG. 3) affixed to the lock and turned when the key is turned in the lock. The cams 56, as shown, are generally oval in shape, but the shape is not critical. It is important, however, that the cams have a dimension in one direction exceeding any other dimension so that, when the cams are turned by the key, the largest dimension is aligned between the recording device 30 and a switch-operating mechanism. The cam member then is effective to operate both of them. The locks 24 are commercially available items and can be obtained from Chicago Lock Company, Chicago, Illinois, by way of example.

Each of the recording devices 30 is also a commercially available item which can be obtained, for example, from Veeder-Root, Inc., of Hartford, Connecticut. The device includes a mounting bracket 58 rotatably carrying a' central shaft 60 on which are located dials 62 which record the gasoline dispensed in units and tenths, the tenths dial being at one end of the device 30. A connecting means in the form of a bevel gear 64 is affixed to the inner end of the shaft 60 and operates the dials 62, when turned. One full revolution of the shaft 60 represents 1 gallon dispensed. The recording devices 30 for each of the stations are substantially identical, except that the opposite dial units are numbered in opposite directions (FIG. 3) since the opposed shafts 60 are turned in opposite directions.

The bracket 58 is slidably mounted in guide blocks 66 (FIGS. 4 and 6) forming grooves or gibs 68 in which the brackets 58 are slidably held for reciprocable lineal movement, in a horizontal direction. The guide blocks 66 are mounted on part of the mounting plate 46 through fasteners 70.

An outer end plate 72 on the bracket 58 has a generally U- shaped spring 74 (FIG. 3) affixed thereto by a screw 76. A coil return spring 78 is carried in compression on a rod 80 which is threaded in the bracket 58 of one of the recording devices 30 and is slidably received in the bracket 58 of the opposite recording device 30. The spring 78 thereby urges the opposed recording devices 30 outwardly with the U-shaped springs 74 being in contact with the cam members 56.

The keys in the first and third rows of locks are turned in counterclockwise directions to operate their respective stations and the keys in the second and fourth rows are turned in clockwise directions. This enables the cam members 56 to engage the closed end portions of the springs 74 first and prevents possible damage to the springs. When the keys are turned, the cam members 56 force the springs 74 and the devices 30 in a longitudinal direction toward a central shaft 82 or 83 upon which are located a plurality of connecting means or bevel gears 84 spaced apart in predetermined positions by sleeves 86. Each of the shafts 82 and 83 can be threaded its entire length with the bevel gears 84 also being threaded and turned onto the shaft to the desired position, being held there by the sleeves. Each of the shafts 82 and 83 preferably is rotatably mounted on the plate 46 by spaced bearings 88 located at end portions and, if needed, at an intermediate portion of the shaft.

The lower end of the shaft 82 has a connection 90 (FIG. 3) to which is affixed a flexible shaft or cable 92 (FIGS. 1 and 2). This shaft extends through the lower wall of the housing 36 and into the top of the pump 12 where it is connected to the gasoline pump computer mechanism therein. The connection between the flexible shaft 92 and the computer will vary somewhat, depending upon the type of commercially available pump 12 employed. Most computers have shafts which revolve once for each gallon of gasoline dispensed, with this shaft extending outside the computer. This shaft and the flexible shaft 92 can then be connected together by a sleeve or other suitable means. If the computer shaft does not extend outside the housing of the computer, then an extension for the shaft must first be added, after which the flexible shaft 92 is connected.

At the upper end of the shaft 82 is a bevel gear 94 (FIG. 3) which is engaged with a second bevel gear 96 on a cross shaft 98 supported by bearings 100. The right end of the cross shaft 98 has a second bevel gear 102 engaged with a bevel gear 104 on the upper end of the shaft 83. The second shaft thereby is driven at the same speed as the first shaft, the various bevel gears having one-to-one ratios. Connections similar to the connection 90 can be formed on the ends of the cross shaft 98 and on the lower end of the shaft 83 to provide greater versatility for the positions where the flexible shaft 92 can be connected.

When the flexible shaft 92 is turned one revolution to indicate 1 gallon is dispensed, the tenths dial of the engaged recording device 30 will similarly be turned one revolution to record the dispensing of 1 gallon for any one of the recording devices 30 which has the bevel gear 64 engaged with the bevel gear 84 on the shaft, thereby being a one-to-one ratio between these bevel gears also.

Three switch-operated shafts or rods are located in the housing 36 to operate the three switches 28. The three shafts are identical in construction and only one will be discussed in detail. A first switch-operating shaft 106 is located at the lefthand side of the left-hand row of the locks 24 of the customer stations 22. A second switch-operating shaft 108 is located between the two intermediate rows of the locks 24. A third switch-operating shaft 110 is located to the right-hand side of the right-hand row of the locks. Each of these shafts is aligned with one of the switches 28. The shafts 106-J10 are slidably mounted in bearings 112, there being two bearings near end portions of each shaft and one at an intermediate portion. The

shafts 106-110 shown are threaded throughout their length and have contacting means in the form of flanges 114 adjustably mounted thereon by nuts 116 to be positioned on the shaft such that the cam member 56 will engage and move the shaft longitudinally when the key is turned. This in turn causes the shaft to depress a spring-loaded plunger 118 of the corresponding switch 28 and close the switch as long as the plunger is depressed. This switch in turn is in series with a motor of the dispensing pump in the gasoline pump 12 and readies it for operation when the usual hand-operated switch on the pump 12, if so equipped, is also closed. Gasoline is then dispensed through the nozzle 16 when the handle on the nozzle valve is squeezed in the usual manner.

As the key is turned, the cam member 56 contacts the spring 74 and moves the recording device 30 toward the main shaft 82 or 83. This movement continues until the bevel gear 64 of the device engages the corresponding bevel gear 84, at which time continued movement of the cam member 56 merely compresses the U-shaped spring 74 slightly. The continued movement of the cam member, however, moves the shaft flange 114 and the corresponding one of the shafts 106-110 sufficiently to close the corresponding switch 28. The cam member preferably causes engagement of the recording device 30 prior to the closing of the switch 28 to assure that no gasoline can be dispensed without being recorded. Further, when the key has been turned in the lock to its maximum extent, the cam member 56 is in a position such that the spring 74 will urge the cam member 56 further in the direction in which it was turned by the key to assure that it will not return toward its original position and shut off the switch 28 prematurely.

Fluorescent tubes 120 and 122 (FIGS. 3 and 4) are located along the sides of the housing 36. These provide light therein for reading of the recording devices 30 and also to indicate that the control is operating. A ballast 124 (FIG. 3) is located at an upper portion of the housing for the fluorescent lights.

The operation of the device will be apparent from the above discussion but will be briefly reviewed. When the key is turned in the appropriate lock 24, the cam member 56 is rotated approximately which causes the cam member to push the gear 64 of the recording device 30 into engagement with the bevel gear 84 on the main shaft. In the event, the gears do not initially mesh, the spring 74 will continue to urge the gears into engagement so that as soon as the shaft 82 begins to rotate, the gears will mesh. The cam member 56 also engages the corresponding flange 114 and causes the corresponding one of the shafts 106-110 to move longitudinally, depressing the plunger 118 of the corresponding switch 28 against the force of the internal spring therein and closing the switch. When gasoline is dispensed from the nozzle 16, the main shafts 82 and 83 are turned through the flexible shaft 92 and through the cross shaft 98.

When the lock 24 is turned back to its original position, the switch 28 is turned ofi and the recording device 30 is then disengaged from the main shaft. The recording device will then have recorded cumulatively the amount of gasoline dispensed for that particular user.

From the above, it will be seen that the controlling and recording unit 10 according to the invention is comprised of relatively inexpensive components which can be assembled relatively easily, and is also easy to service and repair. The unit also is relatively maintenance free and incorporates a high degree of reliability in its operation due to its simplicity and minimum number of moving parts subject to wear.

Various modifications of the above described embodiment of the invention will be apparent to those skilled in the art and it is to be understood that such modifications can be made without departing from the scope of the invention, if they are within the spirit and the tenor of the accompanying claims.

We claim:

1. Apparatus for controlling and recording the amount of liquid dispensed over a period of time by each of a plurality of users, each user having a different key, said apparatus comprising a housing adapted for mounting adjacent liquid dispensing means, a first shaft in said housing and adapted to be rotated when liquid is dispensed, with the extent of rotation depending upon the quantity of liquid dispensed, said shaft having connecting means mounted thereon and rotatable therewith, a plurality of recording devices positioned in a row in said housing and having connecting means for operating said recording devices when engaged with the connecting means of said shaft, a second shaft in said housing positioned generally parallel to said first shaft and spaced therefrom, a switch engageable by said second shaft and closed when operated by longitudinal movement of said second shaft, said switch being effective to actuate the dispensing means when the switch is closed, a plurality of contacting means on said second shaft corresponding to the plurality of recording devices, and key-operated cam means mounted in said housing between each of said contacting means and the corresponding recording device and effective to engage the connecting means of the recording device with the corresponding connecting means of said first shaft and for substantially simultaneously engaging said contacting means to cause said second shaft to close said switch when a key of a user is received by said key-operated cam means and is turned.

2. Apparatus according to claim 1 characterized by said recording devices being slidably supported in said housing for lineal movement, said key-operated cam means causing the connecting means of the recording devices to engage the corresponding connecting means of the first shaft by moving the entire recording devices toward the shaft connecting means, and spring positioned between each of the recording devices and the corresponding key-operated cam means to cause the key-operated cam means to resiliently engage the corresponding recording device.

3. Apparatus according to claim 2 characterized further by additional springs associated with said recording devices and urging said recording devices away from said first shaft and into engagement with the corresponding key-operated cam means.

4. Apparatus according to claim 1 characterized by means for slidably supporting said second shaft for longitudinal movement in said housing, said switch being aligned with an end of said second shaft.

5. Apparatus according to claim 4 characterized by said contacting means each comprising a flange extending transversely outwardly from said second shaft and positioned to be in the path of movement of the corresponding key-operated cam means.

6. Apparatus for controlling and recording the amount of liquid dispensed over a period of time by each of a plurality of users, each user having a different key, said apparatus comprising a housing adapted for mounting adjacent liquid dispensing means, a first shaft in said housing and rotated when liquid is dispensed, with the extent of rotation depending upon the quantity of liquid dispensed, said shaft having a plurality of first spaced connecting means mounted thereon and rotatable therewith, a second shaft in said housing spaced from and parallel to said first shaft, means connecting said first and second shafts to cause said second shaft to rotate with said first shaft when the liquid is dispensed, with the extent of rotation of said second shaft also depending upon the quantity of liquid dispensed, said second shaft having a plurality of second spaced connecting means mounted therein and rotatable therewith, a plurality of recording devices in said housing for the users and arranged in two parallel rows which are parallel to said first and second shafts and are positioned between said first and second shafts, each of said recording devices having connecting means for operating the recording device when engaged with one of said connecting means of one of said first and second shafts, a third shaft extending generally parallel to the two rows of said recording devices and located between the two rows, a switch engageable by said third shaft and closed when said third shaft is moved longitudinally in a predetermined direction, a plurality of contacting means on said third shaft spaced therealong and equal in number to the number of said recording devices in either row, and keyoperated means mounted in said housing between each of said recording devices and one of said contacting means and effective to engage the connecting means of the recording device with the corresponding connecting means of one of said first and second shafts and for substantially simultaneously engaging said contacting means of said third shaft to close said switch when a key of a user is received by said key-operated means and is turned.

7. Apparatus according to claim 6 characterized by said recording devices being slidably supported in said housing for lineal movement, said key-operated means causing the connecting means of the recording devices to engage the corresponding connecting means of the first and second shafts by moving the entire recording devices toward the shaft connecting means, and a spring positioned between each of the recording devices and the corresponding key-operated means to cause the key-operated means to resiliently engage the corresponding recording device.

8. Apparatus according to claim 6 characterized by means for slidably supporting said third shaft for longitudinal movement in said housing, said switch being closed by an end of said third shaft.

9. Apparatus according to claim 6 characterized by said contacting means each comprising a flange extending transversely outwardly from said third shaft and positioned to be in the path of movement of the corresponding key-operated means.

10. Apparatus according to claim 6 characterized by said key-operated means each comprising an elongate cam member having a maximum dimension exceeding the distance between the corresponding recording device and the corresponding contacting means and turnable by a key to place the maximum dimension between the corresponding recording device and the corresponding contacting means, each of said cam members also having a minimum dimension which is less than the distance between the corresponding recording device and the corresponding contacting means when the key is removed. 

1. Apparatus for controlling and recording the amount of liquid dispensed over a period of time by each of a plurality of users, each user having a different key, said apparatus comprising a housing adapted for mounting adjacent liquid dispensing means, a first shaft in said housing and adapted to be rotated when liquid is dispensed, with the extent of rotation depending upon the quantity of liquid dispensed, said shaft having connecting means mounted thereon and rotatable therewith, a plurality of recording devices positioned in a row in said housing and having connecting means for operating said recording devices when engaged with the connecting means of said shaft, a second shaft in said housing positioned generally parallel to said first shaft and spaced therefrom, a switch engageable by said second shaft and closed when operated by longitudinal movement of said second shaft, said switch being effective to actuate the dispensing means when the switch is closed, a plurality of contacting means on said second shaft corresponding to the plurality of recording devices, and key-operated cam means mounted in said housing between each of said contacting means and the corresponding recording device and effective to engage the connecting means of the recording device with the corresponding connecting means of said first shaft and for substantially simultaneously engaging said contacting means to cause said second shaft to close said switch when a key of a user is received by said key-operated cam means and is turned.
 2. Apparatus according to claim 1 characterized by said recording devices being slidably supported in said housing for lineal movement, said key-operated cam means causing the connecting means of the recording devices to engage the corresponding connecting means of the first shaft by moving the entire recording devices toward the shaft connecting means, and spring positioned between each of the recording devices and the corresponding key-operated cam means to cause the key-operated cam means to resiliently engage the corresponding recording device.
 3. Apparatus according to claim 2 characterized further by additional springs associated with said recording devices and urging said recording devices away from said first shaft and into engagement with the corresponding key-operated cam means.
 4. Apparatus according to claim 1 characterized by means for slidably supporting said second shaft for longitudinal movement in said housing, said switch being aligned with an end of said second shaft.
 5. Apparatus according to claim 4 characterized by said contacting means each comprising a flange extending transversely outwardly from said second shaft and positioned to be in the path of movement of the corresponding key-operated cam means.
 6. Apparatus for controlling and recording the amount of liquid dispensed over a period of time by each of a plurality of users, each user having a different key, said apparatus comprising a housing adapted for mounting adjacent liquid dispensing means, a first shaft in said housing and rotated when liquid is dispensed, with the extent of rotation depending upon the quantity of liquid dispensed, said shaft having a plurality of first spaced connecting means mounted thereon and rotatable therewith, a second shaft in said housing spaced from and parallel to said first shaft, means connecting said first and second shafts to cause said second shaft to rotate with said first shaft when the liquid is dispensed, with the extent of rotation of said second shaft also depending upon the quantity of liquid dispensed, said second shaft having a plurality of second spaced connecting means mounted therein and rotatable therewith, a plurality of recording devices in said housing for the users and arranged in two parallel rows which are parallel to said first and second shafts and are positioned between said first and second shafts, each of said recording devices having connecting means for operating the recording device when engaged with one of said connecting means of one of said first and second shafts, a third shaft extending generally parallel to the two rows of said recording devices and located between the two rows, a switch engageable by said third shaft and closed when said third shaft is moved longitudinally in a predetermined direction, a plurality of contacting means on said third shaft spaced therealong and equal in number to the number of said recording devices in either row, and key-operated means mounted in said housing between each of said recording devices and one of said contacting means and effective to engage the connecting means of the recording device with the corresponding connecting means of one of said first and second shafts and for substantially simultaneously engaging said contacting means of said third shaft to close said switch when a key of a user is received by said key-operated means and is turned.
 7. Apparatus according to claim 6 characterized by said recording devices being slidably supported in said housing for lineal movement, said key-operated means causing the connecting means of the recording devices to engage the corresponding connecting means of the first and second shafts by moving the entire recording devices toward the shaft connecting means, and a spring positioned between each of the recording devices and the corresponding key-operated means to cause the key-operated means to resiliently engage the corresponding recording device.
 8. Apparatus according to claim 6 characterized by means for slidably supporting said third shaft for longitudinal movement in said housing, said switch being closed by an end of said third shaft.
 9. Apparatus according to claim 6 characterized by said contacting means each comprising a flange extending transversely outwardly from said third shaft and positioned to be in the path of movement of the correspondIng key-operated means.
 10. Apparatus according to claim 6 characterized by said key-operated means each comprising an elongate cam member having a maximum dimension exceeding the distance between the corresponding recording device and the corresponding contacting means and turnable by a key to place the maximum dimension between the corresponding recording device and the corresponding contacting means, each of said cam members also having a minimum dimension which is less than the distance between the corresponding recording device and the corresponding contacting means when the key is removed. 